In various instances it is desirable to utilize a liquid stream to impact upon a solid surface and thus help to remove rust, scale or other solid matter from such surface. The use of such a liquid stream may be particularly desirable in situations where it is difficult to reach the surface to be cleaned, as for instance in large tanks, furnaces and the like. With previously available nozzles a continuing or recurring problem has been a tendency of the fluid stream to fan out or spread apart as the liquid gets further from the point of discharge from the nozzle. The result of such spreading apart of the liquid stream is a reduction in the force applied when the stream impacts on the surface to be cleaned. As a result, it may be necessary to use a larger nozzle or a greater amount of time to achieve satisfactory results.
One application in which such straight stream nozzles are useful is in the cleaning of soot blowers where an elongated member commonly called a lance is provided with a plurality of nozzles and inserted into the blower through one or more openings provided for that purpose. Construction and operation of such apparatus is described in U.S. Pat. Nos. 4,209,028, 4,422,882 and others and need not be described here in further detail.
Various attempts have been made previously to provide improved nozzle designs whereby a liquid stream maintains greater integrity even at substantial distances from the point of discharge from the nozzle. One such prior design is described in U.S. Pat. No. 4,565,324 wherein a plurality of smaller streams are discharged in such a manner as to generally surround a single large central stream. Nozzles in accord with this patent produce a more concentrated and coherent fluid stream than earlier designs but still evidence some stream deterioration, especially at substantial distances from the point of discharge.